Osteoarthritis of the knee is a leading cause of physical disability. Generally, adults who have osteoarthritis of the knee report having some pain, stiffness, or swelling in the knee joint on most days. Osteoarthritis of the knee, along with osteoarthritis of the hip, has a major effect on a person's ability to walk and climb stairs. Here are some frequently asked questions about osteoarthritis of the knee and its effect on a person's life.

In 2001, more than 13.5 million American adults reported having knee joint pain, swelling, and stiffness. Among those with osteoarthritis of the knee, almost half are older than 65 years. Among those in the United States who say they have osteoarthritis of the knee, 88% are white and 9% are African-Americans.

In 2001, people with osteoarthritis of the knee made more than 5.5 million visits to physicians' offices and more than 271,000 outpatient visits for a variety of reasons.

There were between 400,000 and 458,000 inpatient hospital stays for individuals with osteoarthritis of the knee in 1999 (counting all hospital visits for all reasons).

• The average length of stay for these patients was almost 5 days.
• The average charge per hospital stay was $23,746.
• About one in five patients with osteoarthritis of the knee, regardless of the reason for their hospitalization, went to a skilled nursing facility or nursing home after being released from the hospital.
• In 1999, approximately 25% of all adults with osteoarthritis of the knee had some type of surgery. The procedure most frequently performed for patients with osteoarthritis of the knee is a total knee joint replacement.

• More than 40% of people with osteoarthritis of the knee rate their health as "poor" or "fair."
• Almost 28% expect that it is "definitely" or "mostly" true that their health will get worse.
• When adults with osteoarthritis of the knee were asked how they felt all or most of the time during the previous month, about 13% reported "everything is an effort."
• In general, people with osteoarthritis of the knee report a higher degree of emotional distress than adults without arthritis or other health limitations.

• In 1999, about 50% of adults with osteoarthritis of the knee were "unable" or had "much difficulty" crouching, stooping, or kneeling.
• More than 30% of adults with osteoarthritis of the knee were "unable" or had "much difficulty" in walking a quarter of a mile; more than one-fourth were unable to take 10 steps without resting.
• More than 25% were "unable" or had "much difficulty" in lifting or carrying 10 lb.
• In contrast, less than 1% of adults without osteoarthritis of the knee had difficulties in these areas.

In 1999, adults with osteoarthritis of the knee reported that they missed an average of more than 13 days of work for health reasons in the previous year. They also spent an average of almost 18 days in bed because of health reasons. People without osteoarthritis of the knee, however, missed only about 3 days of work and spent 1.5 days in bed for health reasons during the year.

This information is based on the "Improving Musculoskeletal Care in America" Project of the Council on Research, Evidence-based Practice Committee, and Department of Research and Scientific Affairs, American Academy of Orthopaedic Surgeons. The material presented is for educational purposes only and is not intended to present the only, or necessarily best, method or procedure for the medical situations discussed.